Early childhood behavioral problems appear to be increasing, with current estimates ranging from 7% to 25%. This increase in the incidence of young children exhibiting challenging behaviors has resulted in disrupted early childhood classrooms and children being expelled from programs. A recent national study confirms that more children are being expelled from preschool than for all other grades. Further, early aggressive behavior has been shown to predict later poor academic performance, delinquency and chronic offending, drug abuse, depression, and school drop out. Despite some well-developed and standardized programs that have been demonstrated to prevent or ameliorate early childhood behavior problems, many children and families go unserved until children are older, problems reach extremes, and evolve into longstanding and more intractable behavioral issues. Unfortunately, these standardized and evidence-based practices are not widely used because of problems with availability and expense;time commitment needed for training, supervision, and monitoring;lack of infrastructure to sustain the program when trained staff leave;problems with parent engagement;and in terms of serving the most behaviorally at risk children, a lack of behavioral health staff that are trained to work with very young children. Consistent with Goal 4 of the President's New Freedom Commission on Mental Health, we are proposing to develop and test an approach to primary prevention for early externalizing behavior problems that can be feasibly implemented in normative childcare settings where many children first come to the attention of the service system. The overall goal of the proposed project is to develop a transportable "real world" intervention model to decrease the number of children in preschool who require intensive behavioral intervention services, and provide a sustainable mechanism for identifying and appropriately intervening with those who do. The specific goals of this development project are to: 1) identify the predictors of successfully implementing an evidence-based, primary prevention curriculum, to address early childhood externalizing behavioral issues in preschool settings;2) assess the impact of curriculum training and implementation on teacher skills in addressing children's externalizing behavior and overall classroom management;3) assess the impact of the curriculum on the level and rates of children experiencing externalizing behavioral issues in the preschool classroom;and 4) provide a basis for the development of an R01 grant to test the efficacy and financial and logistical feasibility of implementing a primary prevention curriculum to address early childhood externalizing behavioral issues in preschool settings.